Organofunctional group-containing organopolysiloxane is employed as a modifier of organic resins through the former's copolymerization with organic resin monomer. This serves to endow the particular organic resin with the weather resistance, surface water repellency, lubricity, biocompatibility, and gas permeability, which are characteristic of the organopolysiloxanes.
Organopolysiloxanes carrying various types of organofunctional groups are known for the modification of organic resins. For example, one can list in this regard amino-modified organopolysiloxanes, epoxy-modified organopolysiloxanes, methacryloxy-modified organopolysiloxanes, carbinol-modified organopolysiloxanes, and carboxylic acid-modified organopolysiloxanes.
Carboxylic acid-modified organopolysiloxane is effective in the particular case of the modification/improvement of polyamide resins, polyester resins, and so forth, because it is reactive with the starting monomers for these organic resins. However, since the copolymerization reaction between the organic resin monomer and carboxylic acid-modified organopolysiloxane is conducted under severe conditions (high temperatures, strong acid/strong base catalysis, etc.), depolymerization of the organopolysiloxane frequently occurs, and the organic resin will not be modified to the anticipated or expected degree. Given these circumstances, demand has arisen within the arena of modifiers for such organic resins for organopolysiloxane which, by virtur of possessing highly reactive organofunctional groups, would be capable of facile copolymerization with the aforesaid organic resin monomer under mild conditions. Organopolysiloxane carrying an Si-bonded, chloroformyl group-containing organic group, a group which would be very reactive in particular with the starting monomer for such organic resins as polyamide resins and polyester resins, could be expected to be an excellent modifier for such organic resins.
Chloroformyl group-containing organic compounds are generally prepared by the reaction of inorganic halide (for example, thionyl chloride) with organic carboxylic acid. Hydrochloric acid, a protonic acid, is generated as a by-product in this case. When this method is applied to carboxylic acid-modified organopolysiloxane, the silicon-oxygen bond, which has a high degree of ionic bond character, is attacked by the protonic acid, and secondary reactions occur in the form of siloxane bond scission, rearrangement, and redistribution. This makes it impossible to obtain the desired organopolysiloxane carrying the Si-bonded, chloroformyl group-containing organic group in its molecular chain.
In another approach, an addition reaction was attempted between chloroformyl-substituted unsaturated hydrocarbon and SiH-containing organopolysiloxane in the presence of a Group VIII transition metal complex catalyst, but this addition reaction did not in fact proceed and the desired organopolysiloxane carrying the Si-bonded, chloroformyl group-containing organic group in its molecular chain was not obtained.